The present invention relates to a radiation image recording and reproducing method and a radiation image storage panel employed for the same, and more particularly, to a radiation image recording and reproducing method utilizing a divalent emporium activated complex halide stimulable phosphor and a radiation image storage panel employed for the same.
2. Description of Prior Art
For obtaining a radiation image, there has been conventionally employed a radiography utilizing a combination of a radiographic film having an emulsion layer containing a sensitive silver salt material and an intensifying screen. As a method replacing the above-mentioned conventional radiography, a radiation image recording and reproducing method utilizing a stimulable phosphor as described, for instance, in U.S. Pat. No. 4,239,968, has been recently paid much attention. The radiation image recording and reproducing method involves steps of causing the stimulable phosphor to absorb a radiation having passed through an object or having radiated by an object; exciting the phosphor with an electromagnetic wave such as visible light or infrared rays (stimulating rays) to release the radiation energy stored in the phosphor as light emission (stimulated emission); photo-electrically converting the emitted light to electric signals; and reproducing the electric signals as a visible image on a recording material such as a radiographic film or on a recording apparatus such as CRT.
Examples of the stimulable phosphor employed in the above-described radiation image recording and reproducing method, for instance, include a cerium and samarium activated strontium sulfide phosphor (SrS:Ce,Sm), an europium and samarium activated strontium sulfide phosphor (SrS:Eu,Sm), an erbium activated thorium dioxide phosphor (ThO.sub.2 :Er), and an europium and samarium activated lanthanum oxisulfide phosphor (La.sub.2 O.sub.2 S Eu,Sm), as disclosed in U.S. Pat. No. 3,859,527. Further, the above-mentioned U.S. Pat. No. 4,239,968 discloses an alkaline earth metal fluorohalide phosphor having the formula (Ba.sub.1-x,M.sup.2+.sub.x)FX:yA, in which M.sup.2+ is at least one divalent metal selected from the group consisting of Mg, Ca, Sr, Zn and Cd; X is at least one halogen selected from the group consisting of Cl, Br and I; A is at least one element selected from the group consisting of Eu, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Yb and Er; and x and y are numbers satisfying the conditions of 0.ltoreq.x.ltoreq.=0.6 and 0.ltoreq.y.ltoreq.0.2, respectively.
In the above-described radiation image recording and reproducing method, a radiation image can be obtained with a sufficient amount of information by applying a radiation to the object at a considerably smaller dose, as compared with the conventional radiography. Accordingly, the radiation image recording and reproducing method is of great value, especially when the method is used for medical diagnosis.
The radiation image recording and reproducing method, as described above, is very useful for obtaining a radiation image as a visible image. However, it is desired that the sensitivity to a radiation of the method is further enhanced to decrease the exposure dose for a human body and facilitate the procedure for converting the stimulated emission to electric signals. Especially when the radiation is applied to a human body, the enhancement in the sensitivity to a radiation is of much value from the viewpoint of adverse effect of the radiation on the human body, even if the level of the enhancement is not so remarkable.